Yes content does matter.
Just about everything has proteins in it, but the human body uses specific groups of amino acids that are not present in every food. Things such as whey protein, eggs, cheese, and meat have highly similar amino acid contents to the ones our body needs/uses. You can eat all the soy beans you want, but your body won't use alot of the protein content in it. Also, if you aren't being very active you get plenty of protein from a normal diet, but if you are climbing, running, lifting or skiing just about every day, your body needs more to rebuild ripped up muscles. Go with high quaity protein, but it won't do shit if you don't put in the work.